1. Field of the Invention
The invention relates to liquid treatment apparatus, and more particularly to clarifiers for use in the separation of solids suspended in water or waste water to provide clarified water.
2. Reference to Prior Art
Clarifiers are used in water and waste water treatment processes for the separation of suspended solids in the water or waste water to provide clarified effluent. As used herein, "waste water"includes water, waste water, and any other liquid to be treated. Waste water typically enters the tank of such a clarifier through an influent trough. In the tank, heavy waste solids settle to the bottom and form a sludge layer, which is removed from the tank by collectors. Light waste materials rise to the surface and are skimmed off. Clarified water flows over a weir into an effluent trough and is discharged.
Clarifiers are commonly either circular or rectangular in shape. An advantage of rectangular clarifiers over circular clarifiers is that arrangements of a plurality of rectangular clarifiers generally require less land area for constructing a given treatment facility than circular clarifiers because rectangular clarifiers can be arranged in closer proximity than circular clarifiers. For example, a plurality of rectangular clarifiers can be arranged side by side in a row. Rectangular clarifiers arranged side by side can share common walls and other common components. Therefore, it is often desirable to utilize rectangular clarifiers due to space and cost considerations. The prior art rectangular clarifiers commonly include an influent trough on one sidewall and an effluent trough located on an opposite sidewall, so that water flows into the tank from the influent trough on one side, across the tank, and out of the tank through the effluent trough on the opposite side.
Some prior art circular clarifiers have demonstrated advantage over prior art rectangular clarifiers by providing more efficient separation than the rectangular clarifiers of a similar surface area. This advantage is primarily attributable to different hydraulic characteristics between those prior art circular clarifiers and prior art rectangular clarifiers. A principal cause of their different hydraulic characteristics is that those circular clarifiers and prior art rectangular clarifiers utilize different influent and effluent trough arrangements. Some circular clarifiers have included trough systems wherein the influent and effluent troughs are proximate each other along the periphery of the clarifier. Such a trough system is described in U.S. Pat. No. 3,717,257 issued to Boyle on Feb. 20, 1973. In such circular clarifiers, water flows into the tank from the peripheral influent trough toward the center of the circular tank, and then flows toward the center and then back to the effluent trough.